The present invention relates to a method and a machine for making an article presenting a secret code hidden by a layer of opaque removable material.
The present specification refers, but without thereby adhere restricting the scope of the invention, to articles made of paper or plastic, such as cards, coupons, tickets or tokens having a certain monetary value and distributed by private or public service organizations. More specifically, this specification refers, purely by way of example, to phone recharge cards which, as is known, have on them a secret numeric code hidden by a layer of opaque, removable material. The latter usually consists of a film of scratch-off ink, which disintegrates into minute particles when scratched and which can be scraped off the paper using a blade, coin or similar item.
The ink film may be applied directly to the paper or to one side of transparent plastic label whose other side has a permanent adhesive on it, by which it sticks to the card in such a way as to cover the code. In both cases, the only way of exposing the code to view is by scraping off at least part of the ink film, which means that it is easy for anyone looking at the card to see whether someone else has already gained access to the code.
Although both methods of hiding the code have been widely adopted because of their simplicity, relatively inexpensive machines are now readily available which can be used to restore the layer of ink for fraudulent purposes.